This invention relates to a method of producing copolymers of cyclopentene, and to novel copolymers of cyclopentene. More particularly, this invention relates to two component copolymers consisting of cyclopentene and a polycyclic olefin, and to three component copolymers consisting of cyclopentene, polycyclic olefin and monoolefin, and a method for producing same.
Recently, polymers obtained by the polymerization of cycloolefin, especially 1,5-trans-polypentenamer obtained by ring opening of cyclopentene has been widely discussed as a new elastomer and is well known for its characteristic properties. However, since the polypentenamer has an essential structure of trans-configuration and accordingly has a tendency to easily crystallize, one defect of this polymer as an elastomer is loss of its elastic property by crystallization when exposed to an atmosphere of low temperature. Moreover, although the processability of a cyclopentene homopolymer having a relatively low molecular weight such as Mooney viscosity in the range of 40 to 80, is not so poor, the processability of a cyclopentene homopolymer having a Mooney viscosity of about 100 to 150 and accordingly having special feature of the polypentenamer is considerably poor. Further, the tear resistance of the homopolymer is rather small for practical use. As is well known, increase of low temperature proof property can be achieved by decreasing the degree of crystallization and by retardation of crystallization velocity. However, it was impossible to improve the low-temperature proof property of the homopolymer by use of conventional techniques. For example, although the resistance to low temperature is expected to improve when the content of the cis-configuration in the homopolymer is increased, experimental results show that such an effect can not be achieved unless the content of cis-configuration is considerably increased. However, such increase results in sacrifice, usually to a fatal degree, of other necessary properties.
In the prior art, there are two methods of copolymer production. One is a method of copolymerization charging two kinds of monomers at the beginning of the polymerization. Another is a method applying a random rearrangement reaction between two kinds of homopolymers in the presence of a random rearrangement catalyst such as tungsten.
Using the former method, a polycyclic olefin may be chosen as a component of copolymer, since its reactivity compared with that of cyclopentene is generally greater and since its ability to coordinate to tungsten which may be used as an active component in a catalytic system, is different from that of cyclopentene. In that case, it is very difficult to prepare a copolymer of uniform composition in molecular structure. The distribution of composition in the polymer molecule and the sequence distribution are seen to have a tendency to be very broad. Further as disclosed in Unexamined Japanese Patent Public Disclosure Ser. No. 47(1972)-3534 and Examined Japanese Patent Publication Ser. No. 47 (1972)-5823, there exists a side reaction which increases the molecular weight of copolymers, or its Mooney viscosity, remarkably in the copolymerization reacting containing a polycyclic olefin as a component of copolymer. Moreover, there is no improvement of physical properties of the resulting copolymer.
Using the latter method, as seen in the Examples disclosed in Unexamined Japanese Patent Publication Ser. No. 48(1973)-12383, there exists a side reaction which breaks down the main chain of the original polymers, thereby generating degradated molecules of low molecular weight. This prevents the rearrangement reaction from continuing for a sufficient time. Moreover, the process itself is disadvantageous, since it is necessary to mix two viscous solutions of two polymers in order to react them to each other. Furthermore, another undesirable side reaction, such as isomerization from cis to trans, also occurs and hence no desirable copolymer can be obtained practically.